Seven Yemenis were released in exchange for Saudi Cpl Jaber al-Kaabi, according to the official Saudi Press Agency.

The coalition said the swap was part of a deal brokered by Yemeni tribal leaders and included a "state of calm" along the Saudi-Yemeni border.

The deal is one of the most hopeful signs yet to emerge from the conflict, which has killed some 6,000 people.

The coalition said it had agreed "a state of calm on the Yemeni border adjacent to [Saudi Arabia] to make way for the entry of medical and relief materials".

The Saudi-led coalition has been carrying out airstrikes in Yemen since March 2015 in support of the internationally-recognised government of President Abedrabbo Mansour Hadi, who has been based in the southern city of Aden since July.

In a leaked report last month, a UN panel of experts accused the Saudi-led coalition of targeting civilians with air strikes in a "widespread and systematic" manner.

The panel said civilians were also being deliberately starved as a war tactic.

Human rights groups have also said that the already dire humanitarian situation in Yemen has deteriorated severely, with more than 21 million people, or four-fifths of the population, now requiring aid.